 In the early 1950s he wrote scenarios for André Franquin's series "Spirou et Fantasio", and Jijé's "Jerry Spring", before he took over the writing of "Tif et Tondu" from Luc Bermar, collaborating with Will over a period of thirteen years.As "Spirou" took to publishing the mini–récit (mini story booklets) Rosy had a hand in the creation of new series that began in this format, and in 1959 Rosy worked with Jean Roba to create the series "Boule et Bill".In 1961 he collaborated with Paul Deliège to create Bobo.